Insert a Node at the end of Doubly Linked List

Last Updated : 07 Aug, 2024

Given a Doubly Linked List, the task is to insert a new node at the end of the linked list.

Examples:

Input: Linked List = 1 <-> 2 <-> 3, NewNode = 4
Output: Linked List = 1 <-> 2 <-> 3 <-> 4
Input: Linked List = NULL, NewNode = 1
Output: Linked List = 1

Approach:

Inserting at the end involves traversing the entire list until we reach the last node. We then set the last node’s next reference to point to the new node and new node's previous reference to point to the last node. Thus, making the new node the last element in the list.

Insertion-at-the-End-in-Doubly-Linked-List — Insert node 4 at the end of Doubly Linked List

Steps to insert a new node at the end:

If the linked list is empty, we set the new node as the head of linked list and return it as the new head of the linked list.
Otherwise, traverse the entire list until we reach the last node, say curr.
Then, set the last node’s next to new node and new node’s prev to last node, making the new node the last element in the list.

C++

// C++ Program to insert a node at the end of doubly linked list  #include <bits/stdc++.h> using namespace std;  struct Node {     int data;     Node *next, *prev;      Node(int new_data) {         data = new_data;         next = prev = nullptr;     } };  // Function to insert a new node at the end of doubly linked list Node *insertEnd(Node *head, int new_data) {      // Create a new node     Node *new_node = new Node(new_data);      // If the linked list is empty, set the new node as the head of linked list     if (head == NULL) {         head = new_node;     }     else {       	Node *curr = head;         while (curr->next != NULL) {             curr = curr->next;         }          // Set the next of last node to new node         curr->next = new_node;          // Set prev of new node to last node         new_node->prev = curr;     }      // Return the head of the doubly linked list     return head; }  void printList(Node *head) {     Node *curr = head;     while (curr != NULL) {         cout << curr->data << " ";         curr = curr->next;     }     cout << endl; }  int main() {      // Create a harcoded doubly linked list:     // 1 <-> 2 <-> 3     Node *head = new Node(1);     head->next = new Node(2);     head->next->prev = head;     head->next->next = new Node(3);     head->next->next->prev = head->next;      // Print the original list     cout << "Original Linked List: ";     printList(head);      // Insert a new node with data 4 at the end     cout << "Inserting Node with data 4 at the end: ";     int data = 4;     head = insertEnd(head, data);      // Print the updated list     printList(head);      return 0; }

// C Program to insert a node at the end of doubly linked list  #include <stdio.h>  struct Node {     int data;     struct Node *next;     struct Node *prev; };  // Function to create a new node with the given data struct Node *createNode(int new_data) {     struct Node *new_node = (struct Node *)malloc(sizeof(struct Node));     new_node->data = new_data;     new_node->next = NULL;     return new_node; }  // Function to insert a new node at the end of the doubly linked list struct Node* insertEnd(struct Node *head, int new_data) {     struct Node *new_node = createNode(new_data);      // If the linked list is empty, set the new node as the head     if (head == NULL) {         head = new_node;     } else {         struct Node *curr = head;         while (curr->next != NULL) {             curr = curr->next;         }          // Set the next of last node to new node         curr->next = new_node;         // Set prev of new node to last node         new_node->prev = curr;     }      return head; }  void printList(struct Node *head) {     struct Node *curr = head;     while (curr != NULL) {         printf("%d ", curr->data);         curr = curr->next;     }     printf("\n"); }  int main() {        // Create a hardcoded doubly linked list:     // 1 <-> 2 <-> 3     struct Node *head = createNode(1);     head->next = createNode(2);     head->next->prev = head;     head->next->next = createNode(3);     head->next->next->prev = head->next;      // Print the original list     printf("Original Linked List: ");     printList(head);      // Insert a new node with data 4 at the end     printf("Inserting Node with data 4 at the end: ");     head = insertEnd(head, 4);      // Print the updated list     printList(head);      return 0; }

Java

// Java Program to insert a node at the end of  // doubly linked list  class Node {     int data;     Node next, prev;      Node(int newData) {         data = newData;         next = prev = null;     } }  public class GFG {      // Function to insert a new node at the end of the     // doubly linked list     public static Node insertEnd(Node head, int newData) {                // Create a new node         Node newNode = new Node(newData);          // If the linked list is empty, set the new node as         // the head         if (head == null) {             head = newNode;         }         else {             Node curr = head;             while (curr.next != null) {                 curr = curr.next;             }              // Set the next of last node to the new node             curr.next = newNode;              // Set the prev of new node to the last node             newNode.prev = curr;         }          return head;     }      // Function to print the doubly linked list     public static void printList(Node head) {         Node curr = head;         while (curr != null) {             System.out.print(curr.data + " ");             curr = curr.next;         }         System.out.println();     }      public static void main(String[] args) {                // Create a hardcoded doubly linked list:         // 1 <-> 2 <-> 3         Node head = new Node(1);         head.next = new Node(2);         head.next.prev = head;         head.next.next = new Node(3);         head.next.next.prev = head.next;          // Print the original list         System.out.println("Original Linked List: ");         printList(head);          // Insert a new node with data 4 at the end         System.out.println(             "Inserting Node with data 4 at the end: ");         int data = 4;         head = insertEnd(head, data);          // Print the updated list         printList(head);     } }

Python

# Python Program to insert a node at the end of doubly linked list  class Node:     def __init__(self, data):         self.data = data         self.next = None         self.prev = None  # Function to insert a new node at the end of the doubly linked list def insert_end(head, new_data):   	     # Create a new node     new_node = Node(new_data)          # If the linked list is empty, set the new node as the head     if head is None:         head = new_node     else:         curr = head         while curr.next is not None:             curr = curr.next                  # Set the next of the last node to the new node         curr.next = new_node                  # Set the prev of the new node to the last node         new_node.prev = curr          return head  def print_list(head):     curr = head     while curr is not None:         print(curr.data, end=" ")         curr = curr.next     print()  if __name__ == "__main__":        # Create a hardcoded doubly linked list:     # 1 <-> 2 <-> 3     head = Node(1)     head.next = Node(2)     head.next.prev = head     head.next.next = Node(3)     head.next.next.prev = head.next      # Print the original list     print("Original Linked List: ", end="")     print_list(head)      # Insert a new node with data 4 at the end     print("Inserting Node with data 4 at the end: ", end="")     data = 4     head = insert_end(head, data)      # Print the updated list     print_list(head)

// C# Program to insert a node at the end of doubly linked list  using System;  class Node {     public int Data;     public Node Next;     public Node Prev;      public Node(int data) {         Data = data;         Next = null;         Prev = null;     } }  class GFG {        // Function to insert a new node at the end of the doubly linked list     public static Node InsertEnd(Node head, int newData) {                	// Create a new node         Node newNode = new Node(newData);          // If the linked list is empty, set the new node as the head         if (head == null) {             head = newNode;         }         else {             Node curr = head;             while (curr.Next != null) {                 curr = curr.Next;             }              // Set the next of the last node to the new node             curr.Next = newNode;              // Set the prev of the new node to the last node             newNode.Prev = curr;         }          return head;     }      // Function to print the doubly linked list     public static void PrintList(Node head) {         Node curr = head;         while (curr != null) {             Console.Write(curr.Data + " ");             curr = curr.Next;         }         Console.WriteLine();     }      static void Main() {                // Create a hardcoded doubly linked list:         // 1 <-> 2 <-> 3         Node head = new Node(1);         head.Next = new Node(2);         head.Next.Prev = head;         head.Next.Next = new Node(3);         head.Next.Next.Prev = head.Next;          // Print the original list         Console.Write("Original Linked List: ");         PrintList(head);          // Insert a new node with data 4 at the end         Console.Write("Inserting Node with data 4 at the end: ");         int data = 4;         head = InsertEnd(head, data);          // Print the updated list         PrintList(head);     } }

JavaScript

// Javascript Program to insert a node at the end of doubly // linked list  class Node {     constructor(data)     {         this.data = data;         this.next = null;         this.prev = null;     } }  function insertEnd(head, newData) {      // Create a new node     const newNode = new Node(newData);      // If the linked list is empty, set the new node as the     // head     if (head === null) {         head = newNode;     }     else {         let curr = head;         while (curr.next !== null) {             curr = curr.next;         }          // Set the next of the last node to the new node         curr.next = newNode;          // Set the prev of the new node to the last node         newNode.prev = curr;     }      return head; }  function printList(head) {     let curr = head;     let result = "";     while (curr !== null) {         result += curr.data + " ";         curr = curr.next;     }     console.log(result.trim()); }  // Create a hardcoded doubly linked list: // 1 <-> 2 <-> 3 let head = new Node(1); head.next = new Node(2); head.next.prev = head; head.next.next = new Node(3); head.next.next.prev = head.next;  // Print the original list console.log("Original Linked List: "); printList(head);  // Insert a new node with data 4 at the end console.log("Inserting Node with data 4 at the end: "); const data = 4; head = insertEnd(head, data);  // Print the updated list printList(head);

Output

Original Linked List: 1 2 3  Inserting Node with data 4 at the end: 1 2 3 4

Time Complexity: O(N), where N is the number of nodes in the linked list.
Auxiliary Space: O(1)

Insert a Node at a specific position in Doubly Linked List

mrityuanjay8vae

Improve

Article Tags :

Practice Tags :

Linked List

Insert a Node at the end of Doubly Linked List

Similar Reads